Plastic liners



W. c. RAINER ETAL 3,202,307

PLASTIC LINERS Aug. 24, 1965 Filed Deo. 3l, 1954 INVENTORS W/LL/AM C. RAINER JOSEPH 6.6`ERMAK JAMES R HAM/70N ARTHUR WSLOA/V W/LL/AM. STEWART KAR/ ASCHELLE/VBERG United States Patent Office 3,202,367 Patented Aug. 24, 1955 3,202,307 PLASTIC LNERS William C. Rainer and Joseph G. Germak, Baltimore, and James l. Hamilton, Glen Burnie, Md., and Arthur W. Sloan, William D. Stewart, and Karl A. Schellenberg, Alexandria, Va., assignors to Crown 'Cork & Seal Company, Inc., Baltimore, Md., a corporation of Maryland Filed Dec. 31, 1954, 'Ser'. No. 478,986 6 Claims. (Cl. 2l5-"39) This invention relates to closures, particularly to closures of the crown type.

The cushion sealing liner for crown type closures is conventionally made of cork. While cork has many desirable properties, which render it an excellent cushion liner, it has the disadvantage that a large part of the cork supply must be imported.

Accordingly, a primary object of the present invention is to provide a substitute for cork as a cushion liner for crown type closures.

Another object of the invention is to prepare a cap having an improved plastic cushion liner.

A further object is to prepare a synthetic cushsion liner having all the desirable properties of cork for this purpose.

A still further object is to reduce bottle leakage by providing a cap having a cushion liner which is somewhat llowable under capping pressure.

Another object of the invention is to provide a cap having a cushion liner which will adhere to the metal surface of the cap or to the conventional lacquer coating on the interior of the cap shell or which will adhere to an adhesive applied on the metal or lacquer coating.

p An equally important object is to provide a cap having` a liner which will be inert with respect to' a variety of foods, beverages and medicinals, and which will not impart taste, odor or color to the contents of the bottle.

A further object is to provide a cap and cushion liner that can be formed on conventional machinery.

While the present invention is primarily directed to making caps of the crown type and it is in this form that it nds its greatest utility, it also is useful in preparing caps of the screw-on, lug or press-on type.

Still further objects and the entire scope of applicability of the present invention will become apparent from the detailed description given hereinafter; it should be understood, however, that the detailed description and specic examples, while indicating preferred embodiments -which approach and, in some cases, even excel cork as cushion liners, more especially as cushion liners for crown A.with cork crown liners.

type shells. While several dilferent types of material have been found to be satisfactory as cushion liners, it should be understood that these materials are not necessarily equivalent, as in many cases, they have dilferent properties, varying degrees of eiectiveness and are prepared in different Ways. These differences will become evident during the subsequent description in the specification.

For the two eXtreme conditions normally encountered in bottle use with crowns having cork liners, the following ranges of values have been found:

Temperature F.) 30-170 Bottle, pressure (p.s.i.) 0-120 Load on crown (total force (tension) inthe side wall of the steel crown when the bottle is under pressure) (lbs.) 62-1625 Load on liner (total force on the gasket liner when the bottle is under pressure) (lbs.) 62-61{ Stress in crown (tensile stress in steel of side wall of crown) (psi.) 1800-3000 Pressure in liner (compressive stress) (pressure in gasket) (psi.) 240-237 Compression in liner made of cork (percent.) 60-58 From these figures, it is evident that the compressibility of the conventional cork liner, in comparison with the compressibility of the crown, is so high that there is very little change in the compression of the liner with variation of the bottle pressure. The large compression of the cork liner and its relative independence of internal pressure contribute materially to its sealing abilities. i

It has been found that it is desirable for a cork substitute to be a soft, compressible material. It has also been found that a closed-cell foamed polymeric material is particularly desirable, as it can be varied in compressibility and hardness to meet varying requirements simply by adjusting the amount of foaming agent. Additionally, it is less dense than unfoamed resin and, hence, is more economical to use than the corresponding unfoamed resin or rubber. Again, not every foamed material can be employed, but only those materials which have the lnecessary combination of properties, such as those above outlined. Neoprene (polychloroprene) was tested as a liner in a conventional metal crown. The neoprene liner of slightly smaller diameter than the crown cap was molded into the cap, using a conventional molding die employed The neoprene proved to be an excellent liner, even in the absence of an adhesive. Six ounce bottles, containing Coca Cola, Seven Up and Carbonated Water, having a 0.066 A inch thick neoprene liner, were cycled daily between 34 F. and 167 F. for

seven days. There was no leakage in any of the bottles.

The neoprene liners employed had been prepared by curing, in the absence of sulfur, the following composition:

Neoprene GN (non-staining) 100 MgO (Heavy) 4 Furnace Black (semi-reinforcing) 100 Dibutyl phthalate 15 Zinc oxide (fast curing) 5 The proportion of neoprene to the other materials is open to considerable variations. Thus, there can be used 0 to 150 parts of furnace black or other conventional filler; 0 to O parts of dibutyl phthalate or other conventional modifier; 4 to 15 0 parts of Mg() or equivalent material and 0 to 100 parts of zinc oxide per 100 parts of neoprene.

The variation in pressure between individaul bottles was small, evenfor highly carbonated beverages.

Plastisols or paste resins, based upon polymers and copolymers of vinyl chloride (which, it should be noted, is an ester) also have been found to be effective as liners. However, not all of these plastisols were equally effective. There are significant variations, depending upon the type of polymer and type and amount of plasticizer and, to some extent, the type of ller.

AV plastisol may be described as being a mixture of a resin or other high polymer with a plasticizer in which it is essentially isoluble at room temperature or very slowly soluble at room temperature, but in which it is essentially completely soluble at some elevated temperature or slowly soluble on standing at room temperature. When such a mixture is heated, the resin dissolves in the hot plasticiZer and, when the solution cools, a permanent gel is formed.

Of the plastisols based on polyvinyl chloride or its copolymers, the most effective ones were prepared from Exon 654 and Vinylite QYNV. Plastisols of Pliovic AO, Vinylite VYHH, and Marvinol MX 3001, were in some instances, too viscous for the incorporation of fillers. It is desirable for commercial use, that the resin should be capable ofV dilution with relatively inexpensive fillers. Plastisols of Geon 121 were approximately ten times as viscous Brookfield viscosimeter) as those of Exon 654 and Vinylite QYNV at the same ratio of resin to plasticizer. Santizer B16 (butyl phthalyl butyl glycolate) and 141 (an arylalkyl phosphate) gave plastisols of lower viscosity than E- ethyl phthalyl ethyl glycolate) and M-17 (methyl phthalyl ethyl glycolate) and, hence, are more desirable than the latter two plasticizers. Santicizer B16 plastisols, when cured, produced products with better physical properties than 141.

Acetyl tributyl citrate and diisobutyl adipate are both excellent plasticizers. Di-Z-ethylhexyl phthalate also was good, but it imparted in some cases an odor to 0.075

inch sheets cured at '150 C. for one minute. Acetyl tributyl citrate imparted no odor, but gave clear strong sheets. Dioctyl phthalate (di-Z-ethylhexyl phthalate) also gave clear strong sheets.

The formulation employed for preparing these sheets and for measuring the viscosities previously mentioned Parts Exon 654 100 Plasticizer 125 Calcium stearate 3 When measured at 37 to 40 C., the viscosities obtained with various plasticizers in the above formulation are given in Table I below. i

4 TABLE i Plasticizer: Viscosity, c.p.s. Santicizer B-16 940 Santicizer E-15 3,750

Santicizer M 17 250,000

Santieizer 141 340 Di-Z-ethyl hexyl phthalate (DOP) 380 Acetyl tributyl citrate 480 Diisobutyl adipate 410 more primary plasticizers with one or more Secondary,v

plasticizers.

The fillers yielding the lowest viscosity of plastisol and the best properties on curing are talc, Fullers earth and:

calcium carbonate. Cork nes can be employed for certain purposes as a filler. Other operative fillers are inorganic materials, such as mica, clay, fibrous magnesium silicate, zeolites, glass iibers, carbon black, powdered charcoal, SiO2 and diatomaceous earth, and organic materials,

such as wood flour, lignin, lignin sulfonates, paper pulp, regenerated cellulose, finely ground straw, finely divided barks, such as Douglas r bark or any fraction thereof, especially the cork fraction, shell, Hours, eg., walnut shell flour and other vegetable matter.

Good stabilizers are Thermolite 31`(thio organic tin compound), and Stayrite (a mixture of metallic soaps, predominately calcium, aluminum and zinc Lstearates with a minor amount of other fatty acid salts) and alkyl and aryl thin compounds, dibutyl tin oxide, calcium, magnesium and aluminum and zinc soaps used singly or in combination. Salts of the higher saturated fatty acids, e.g., stearic acid, are preferred. Tin compounds, such as dibutyl tin oxide, are also eiiicacious. Sodium phosphate, cadmium and barium epoxy compounds, diphenyl urea, and alphaphenyl indole are also good. Calcium stearate was satisfactory when employed at concentrations of 3% on the resin. Other conventional stabilizers for the vinyl chloride resins, such as those recited in Schildknecht Vinyl and Related Polymers (1952) can also be used.

The proportions of the Various materials, preferably should be in the following range:

Parts Vinyl chloride polymer or copolymer Plasticizer 60 to 150 Filler Oto l5() Stabilizer 1 to 10 When a ller is employed, preferably it is present in an amount of 20 to 100 parts per 100 parts of resin.

Prefrably, at least 100 parts of plasticizer are employed per 100 parts of resin.

Unichrome 219 PX (a butadiene-acrylonitrilerubber" lacquer) was found to be an excellent adhesive for bonding polyvinyl chloride plastisols to either lacquered or unlacquered crown caps. For best results, the Unichrome, as a 1 to 10 solution in acetone, or Goodrich A 458B should be applied to the metal and then baked minutes at 170 F. Other satisfactory adhesives include chlorinated rubber (Parlon), copolymers and terpolymers of vinyl chloride with monomers containing polar groups, e.g., vinyl acetate (this may be partially hydrolyzed later to obtain OH groups for linking the polymer to metal through isocyanate groups (especially triisocyanates) acrylonitrile, dialkyl maleates (e.g., diethyl maleate), dialkyl fumarates (e.g., dissopropyl fumarate), and polyurethanes, e.g., (adipic acid reacted with excess ethylene glycol then with p,p diphenyl methane diisocyanate). Other good adhesives are neoprene, blends of polyvinyl chloride and butadiene-acrylonitrile polymers (latex), cyclized natural rubber, e.g., Vulcalock.

B. F. Godrich adhesive A 458B, Hycar-phenolic lacquer (rubbery butadiene-acrylonitrile and phenolformaldehyde blend) is an excellent adhesive for bonding polyvinyl chloride to lacquered and unlacquered steel plate. It is as good as Unichrome 219 PX for bonding to unlacquered shells and even better as an adhesive for lacquered shells. For satisfactory bonding, the plastisol should be cured at 170 C. In typical tests, the results were as follows. The value of adhesive Was based on the force required to pull the strips apart.

Adhesive Metal Baking Results 1. A 4583-.... Plain None Fair. 2. A 458B Laequered-- do ood. 3. A 45813.... Pla' 170, 10 min.-. Very good.1 4. 170, l0 min- Do.1 5. 17g; 10 min.-. G lo. 6. 17 ,10 min oo 7. Unichrome 170. 10 ruin." Very 5006.1

followed by A 458B. Laequered.- 170, 10 mim-, Do.l 8. A 458B followed by Plain 170, 10 mm--. Good.

Uuichrome. Lacquered 170, 10 min. Do.

1 The borided strips of metal could not be separated by hand-pull.

The conventional lacquers can be employed in forming lacquered caps. One such lacquer is a vinyl lacquer, eg., 80% of a vinylchloride-vinylacetate copolymer (87% vinylchloride) together with 20% of an oleoresinousrnodier, e.g., tung oil modiled phenyl phenol-formaldehyde, dissolved in an organic solvent, such as 70% xylene and 30% isophorone with 20% solids. More volatile solvents, such as toluene, methylethyl ketone and methyl isobutyl ketone can also be employed. As an alternative lacquer there can be used 80% of a vinylchloride-vinyl acetate-maleic anhydride terpolymer prepared from monomers in the respective ratios of 87 :12:1 together with 20% of an o-cre-sol-formaldehyde'resin dissolved in any of the above mentioned solvents or mixture of solvents. Especially effective liners have been made by foaming polyvinylchloride plastisols with blowing agents to give preferably closed-cell products. Sheets of uniform porosity can be obtained with water and bicarbonates, e.g., sodium and ammonium bicarbonates or by using carbon dioxide or other inert gas under pressure, or supersaturated solutions of carbon dioxide or other inert gas in the liquid phase of the plastisol. Other foaming agents which can be used are potassium bicarbonate, ammonium nitrate,

barium nitrite, azo, compounds, eg., diazoaminobenzene, BL-353 and azobisisobutyronitrile (Porofor N), sodium formate, ammonium benzoate; alpha, alphaazobisbutyronitrile, 1,3-bis(oxenyl)triazene, 1,3-bis (p-xenyl) triazene, sodium bicarbonate mixed with a higher fatty acid, e.g., oleic acid, isocyanates, e.g., 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, or phenyl mono isocyanate mixed with water. Other blowing agents are hydrazine, hydrazine hydrate, hydrazine salts, e.g., hydrazine acetate, oxalate, acetate, phosphate, formate,` salicylate, malonate, stearate and sulfate, hydrazides of organic sulfonic acids, e.g., p-toluene sulf'onio acid hydrazide, propane sulfonic acid hydrazide, urea oxalate, a urea and biuret mixture, nitroso compounds, such as dinitrosopentamethylene tetramine (Unicel D), N-nitroso beta amino ketones, c g., N-nitroso triacetone amine, N- methyl N-nitroso diacetone amine (the nitroso amines are preferably used with a basic accelerator, eg., triethanolamine), diphenyl4,4di(sulfonyl azide), azosulfones, arylazotriaryl methanes, bicarbonates, e.g., sodium bicarbonate, mixed with cyanamide and its polymers, such as dicyandiamide and melamine; cyclic ethylene carbonate, organic peroxides, eg., benzoyl peroxide, dini-` troso pentamethylene tetramine, bis benzene bis(sulfonyl hydrazide), Vynafoarn 8910 (a mixture of Pliovic AO and a blowing agent).

Toxic and hazardous foaming agents should be avoided for food uses.

The foaming agent is normally used in an amount of 1 to 20%, based on the polyvinyl chloride or other polymer in preparing foamed sheets. When water is used in the foaming composition, non-toxic emulsifiers, such as non-ionic detergents, including sorbitan, sesqui-oleate, sorbitan monostearate (Span 60) (relatively poor), glycerol mannitan laurate (Atlas NNO), (very good), polyoxyethylene sorbitol cleats-laurate (Atlas 1045A) (very good), sorbitan laurate,the Tweens, i.e., ethylene oxide condensation products or sorbitan and mannitan esters of higher fatty acids may be used. In general, nonionic detergents with a high hydrophiliclyolphilic balance may be used, eg., polyoxyethylene stearate, polyoxyethylene sorbitol-laurate, polyoxyethylene sorbitan monopalmitate and the corresponding mono-oleate and monolaurate, as well as the corresponding trilaurate, trioleate and tristearate, alkyl phenol-alkylene oxide condensation products, p-isooctyl phenol-lO-ethylene oxide and Tergitol NPX are examples of this type of detergent, dodecyl alcohol-l6-ethylene oxide, polyethylene glycol esters of higher fatty acids, such as Acco Emulsiiier No. 5, glyceryl mono-stearate, propylene glycol monostearate (Aldo 25), glycerol oleo-stearate, polyoxyethylene lauryl ether (Brij-35). Anionic detergents also can be used, such as Aerosol OT (dioctyl ester of sodium sulfosuccinic acid), sodium salt of dihexyl sulfosuccinate, Aersol 18 (n-octadecyl sodium sulfosuccinate), sodium lorol sulfonate, sulfonated fatty acid amides and fatty alcohol amine sulfates. Mixed cationic-anionic detergents, such as N-dodecyl beta-alanine can be employed as can straight cationic detergents, such as cetyl pyridinium chloride and bromide, diisobutyl-phenoxy-ethoxy ethyl dimethyl ben-` zyl ammonium chloride and other quaternary ammonium halides, long chain fatty acid amides containing multiple amine groups, eg., Intracol O, alkyl polyoxyethylene glycol amines, alkylat-ed amides, eg., Michelene 20, can be employed in amounts from 0.025% to 5 based on the polyvinyl chloride.` (All parts and percentages in the specification and claims are by weight, unless otherwise indicated.)

ln place of foamed polyvinyl chloride plastisols, less preferably other foamed polymers can be used, such as polystyrene, plastisols from cellulose ethers, eg., ethyl cellulose and cellulose esters, e.g., cellulose acetate and cellulose nitrate. Cellulose acetate-butyrate and cellulose acetate-sorbate plastisols` are considerably better than aaoaso'? straight cellulose acetate plastisols in performance, toluene diisocyanate NGO NGO

or similar isocyanate modified polyesters tthese are prepared by reacting toluene diisocyanate with polyesters having hydroxy end groups) eg., ethylene glycol or propylene glycol adipic acid polymers. Other examples of foamed polymers are polyvinyl butyral, polyethylene (under controlled conditions), terpolymers, e.g., maleic acid reaction products of copolymers of vinyl chloride with vinyl acetate, trichloroethylene, alkyl acrylates, eg., methyl or ethylacrylates, vinylidene chloride, dialkyl maleates, e.g., dimethyl or diethyl maleate, diethyl furnarate, diethyl chloro maleate, acrylonitrile, divinylbenzene or copolymers of any of these unsaturated compounds with vinyl chloride rather than terpolymers can be employed, copolymers and terpolymers of styrene with any of the above monomers or with small amounts of unsaturated oils, e.g., tung oil and oiticcia oil, polyvinyl acetals, e.g., polyvinyl butyral, styrene-butadiene copolymers, eg., GR-S, polyisoprene, isoprene copolymers, polyvinylidene chloride and copolymers of vinylidene chloride with any of the above monomers, styrenated alkyd resins, polyisobutylene, polyurethanes, linear polyamides, eg., polymeric hexamethylene adipamide, polyesters, e.g., polymeric ethylene terephthalate, and blends of condensation of polymers with natural or synthetic rubber.

The preferred polymers as indicated are polyvinyl chloride and copolymers of vinyl chloride with not more than 10% and usually not more than 5% of a copolymerizable ethylenically unsaturated monomer.

The curing cycles for filled, unlled and foamed plastisols of polyvinyl chloride embrace the following ranges:

Mold temperature C-- 100 to 200 Curing time minutes M30 to 5 Mold pressure z lbs/sq. inch-- to 10,000

The preferred conditions for curing sheets from which the liners are cut are:

Mold temperature C-- 130 to 200 (Most preferably, 170 C.)

Curing time seconds l to 30 Mold pressure lbs/sq. inch 100 The liners are cut from the sheet, eg., by a cutting die, and preferably, have a diameter less than that of the undersurface of the top of the crown shell. The liners are simultaneously positioned and centered in the shells. The shellsmay be heated, eg., to a temperature of 200 to 300 F. to render the bottom surface of the disc sufficiently tacky to adhere the disc to the shell. Then, the liners are subjected to a molding pressure of about 100 lbs/sq. inch to 500'lbs./sq. inch. The molding die, preferably, hads a stepped face and can be a plunger of the type conventionally employed in the crown cap art to produce a liner having a central recess and a relatively thicker rim 'adjacent the skirt Wall, so as to provide a greater amount of inner material for engagement with a lip of a bottle to insure an adequate seal. This method of molding also reduces the amount of material required in the disc, the amount in the center ofthe liner constituting merely a thin coating serving the same purpose as the well known crown center spot. The molding die or plunger also may be heated, eg., to 150 to 300 F. lf desired, the molding plunger can be a conventional one without the step. In such case, the final crown will not have a center recess;

instead of curing the unfoamed plastisol in the cap, it is frequently advantageous to partially or completely cure the plastisol as a button or disc (usually solid) of the proper Weight. be carried out for example as the buttons travel on an endless belt through a heated oven or as they travel around heated forming plates. Each button is then inserted into an individual crown cap, either cold or, pref-V erably, while still hot. By using a preheated cap and a preheated plunger for shaping the liner, the button is pressed into the desired shape in a very short time. In the case of partially cured buttons, the simultaneous completion of the cure is accomplished. Surprisingly, it has been found that, even a fully cured button of a polyvinyl chloride plastisol, e.g., from parts of Exon 654, 125 parts Santicizer B 16 and 3 parts of calcium stearate, can be reshaped, e.g., at 180 C. in a crown cap with the preheated plunger. The cured plastisol assumes the new shape with no tendency to return to its original shape on cooling. The use of pre-cured plastisols in units of the proper size has the advantage over curing the plastisol in the cap in that the curing of the plastisol need not be synchronized with subsequent insertion of the plastic unit into the crown cap followed by the shaping operation. Consequently, the molding machinery need not'be tied up for as great a length of time as when curing is accom-V plished in the cap shell.

Alternatively, the plastisol can be inserted in the crown in the form of a liquid or paste and cured in place by using a die as above, either or both of the die and crown caps are preferably heated to hasten curing. This method is especially advantageous in preparing foamed liners.

Molding pressure is not normally critical and when foamed liners are formed in situ, using pressurized car. bon dioxide or other inert gas, some leakage should beiV FTGURE 2 is a sectional view of the cap taken along line 2 2 shown in FIGURE l having a liner made from a foamed polymer.

FIGURE 3 is an enlarged broken away sectional View of a cap having a liner made from a foamed polymer.

FIGURE 4 is a broken away sectional view, similar to FIGURE 3, but having an unfoamed polymer liner and without a center recess.

FGURE 5 shows a stepped die about to be applied to a cap containing a plastisol.

ln the drawings, the numeral 10 indicates a metal cap shell of the crown type having a lacquer coating 12 and a polymeric cushion liner 14. rThe polymer can either be foamed 16 (FlGURES 2 and 3) or unfoarned 13 (FIGURE 4). The polymeric material can be molded so as to form a center recess as at Z0, although this is' not essential.

' Referring to FIGURE 5, there is shown a stepped die or plunger 22 about to be applied to a cap 10 having a blob of polyvinyl chloride plastisol 24 in the center thereof in order to spread and cure the plastisol. The die can be heated as by electrical heating element 26.

ln preparing the compositions of the following Table Il, the mixing of the plastisol was elfected by stirring for one minute in an Oster Blender. The viscosity of the. plastisols was measured, immediately after mixing, with a Brookfield viscosimeter, Model RVF. 0.5 grams of each of the plastisol compositions was placed in a conventional crown cap and cured for 10 minutes as C. Y

The partial or complete curing can TABLE II Resm and plaslclzer compositions Composition Parts Viscosity, Temp., Remarks i Centipoises degrees l Geon 121 100 20,000 30 Cure soft, moderately -15 125 tough, full of gas Calcium Stearate 3 bubbles, plastisol set up at room temp., in 4 days. 2 Exon 654 100 3, 750 30 Cure same as #1, vis- -15 125 cosity of plastisol Ca St.- 3 40,000 after 1 day,

set up 4 days. 3 Pliovic AO 100 (l) Cure same as #1.

125 Ca. St 3 4 Marvinol MX 3001 10o (2) Do.

3 5 QYNV Blend 466 100 920 30 Do.

-15 125 Ca. St..." 3 6 VYHH.-. 100 (3) Discarded as unsuit- E-15 125 able for making Ca. St 3 liners. 7 Exon G54 100 940 30 Cure Same as #1.

B-IG. 125 Ca. St... 3 8 Exon 654 100 250,000 D0.

-17 125 Ca St 3 Y 9 Exon 654 100 340 30 Cure soft, moderately Sant'cizer 141-. 125 tough.

a t 3 10..--. QYNV blend 7 1go 1,100 30 Cure same as #1.

5 Ca. St 3 11--... QYNV blend 466. 100 440 28 Cure opaque moder- Santicizer 141 125 A ately tough. Ca. St 3 1 Thick paste. 2 Medium paste, 3 Dry cakey mass.

The characteristics of several ofthe vinyl chloride polymers employed in the above Table II are as follows:

Geon 121 is a polyvinyl chloride having a limiting intrinsic viscosity [1;]0 of 1.2 and a molecular weight of 89,000; Exon 654 is a vinyl chloride-trichloroethylene copolymer (at least 95% vinyl chloride) [1;]0 yof 1.2 and la mol. wt. of 89,000; Pliovic AO is a vinyl chloride-dialkyl maleate copolymer (at -least 95% vinyl chloride); VYHH is a vinyl chloride-vinyl acetate copolymer (87% vinyl chloride) [17]() of 0.44 and mol. -wt. of 20,000.

Other typical vinyl chloride polymers are Geon 101 [n] of 1.13 and mol. wt. 812,000; Geon 202, [77],) of 0.80 and mol. wt. of 49,000; Geon 205 [71]() of 0.51 and mol. Wt. of 25,000; and Vinylite VYNV (copolymer of 95% vinyl chloride-% vinyl acetate) [7;]0 of 1.87 and mol: wt. 174,000. There can be employed a vinyl chloride-trichloroethylene copolymer containing less than of trichloroethylene.

All of the above polymers are capable of forming plastisols. It has previously been proposed to employ polyvinyl chloride plastisols in making liners for crownV caps. However, the prior art Workers never disclosed the molec- -nlar weights or limiting intrinsic viscosity of the polymers. To obtain compositions which can be formed into liners on a commercial scale, we have found that the molecular weight and limiting intrinsic viscosity are of -a critical nature. The limiting intrinsic viscosity [11]@ .should be between 0.50 `and 1.20 and the molecular weight should be between 25,000 and 90,000 to give compositions which can be satisfactorily blended with fillers or readily converted to the cured state upon the application of heat, While, at the same time, not being too readily dissolved in the plasticizer at room temperature.

Any `conventional paste-forming vinyl chloride polymer or copolymer having the requite characteristics can be employed. Copolymers should contain at least 90% of vinyl chloride and, preferably, at least 95% of vinyl chloride.

eizer to resin. The ratio of plasticizer' to resin is preferably bet-Ween 0.6 to 1 and 1.5 to 1 and most preferably is at least 1:11. In any event, the ratio of plasticizer to resin should be such as to give a viscosity `at 30" C. of between 300 c.p.-s. and 25,000 c.p.s., preferably between 900"c.p.s. and 15,000 c.p.s.

The viscosity of the plastisol increases with time after mixing. Part of the increase in viscosity is attributed to thixotropy, since remixing in the blender reduces thefviscosity to almost the original value. Such mixtures which have been allowed to stand can Vbe rei-used after remixing, provided the viscosity then is still in the operative range.

The eiects of plasticizer-resin ratio, temperature and time after mixing are shown in Table III below.

TABLE HI Factors aectng plastisol viscosity 1. Different Plasticizer-resin Ratios.

Calcium Parts B-16 Parts Viscosity Temp. Stearate Exon 654 A A 3 150 100 880 40 B 3 125 100 940 30 C 3 100 100 1,020 36 D 3 75 100 152, 000 30 2. Etlect of Temperature on Mix 1 C above:

Temperature Viscosity 3. Effect of Time after Mixing, Mix 1 C.

Time after Mixing Temperature Viscosity Immediately 36 1, 020 15 minutes- 31 1, 720 1 hour 32 1, 900 2 hours 31 3, 080 Remixing in blender 31 1, 440

Various fillers can be incorporated in the plastisols. To be satisfactory, the filler should not increase the viscosity of the composition beyond the operative range and.V should not adversely affect the cure or adversely affect the adhesion to lacquered crown caps to too great a degree. Among the most satisfactory fillers, as previously indicated, are Fullers earth, talc and calcium carbonate.

The lled compositions described in Table IV below were cured for minutes in crown caps at 170 C.,

l2 without leakage. The same excellent results were obtained by repeating the tests using a lower temperature of 2 C. The pressure for the Canada Dry soda Water bottles ranged from 60 p.s.i. at 26 C. to 165 p.s.i. at 75 C. Soda water was chosen for this test because it presents more rigorous testing conditions, e.g., ability towithstand the development of leaks at higher pressures, than do the cola drinks, for example, in which the pressures developed `are not nearly as high. For example, Iat 75 C. a cola beverage (Coca-Cola) develops a pres-V using 0.5 gram of the composition in each cap. 10 sure of only approximately 115 p.s.i.

TABLE IV Experimental fillers Formulation:

Santicizer B-16 Grams Filler Quantity, Viscosity Temp Cure grams (Brookfield) deg.

1 Glass fiber 25 Very thick past-c Very tough. 2 Glassfloss 5 Medium paste Do. 3 Wood our. 25 Moderately tough,

odor present. 4 do 50 Do. 5 Fullers earth 50 Cure fairly tough,

hard. rln 100 Do. dn 150 Do.

Talc 50 Do. rln 100 Do. dn 150 Do. Tale 1 125 Do. Tale 1 125 }N0 difference cithin 0. 5 noticeable. Y 13 Parlon (chlorinated rubber) 2 50 145,000 Cure opaque, but

rubbcry, tough. 14 #13 50 ml. toluene 2 About same Cure translucent otherwise about same as $13. Darco G-GO, activated carbon 360,000 (thick paste). Cure fair. CaCO3, powdered 2,800 46 Cilire ilairly tough,

lar dn 100 45 D0. do 150 45 Do.

ZnO 50 40 Opaque, white,

l fairly tough, hard. ZnO. 33,000 (solid paste) 10 Fairly tough, hard opaque, white. SiO2, rubber grade l5 Medium paste Fairly tough.

Marasperse CB (calcium sodium lignin sulfonate) 50 1,860 40 Poor adhesion,

' otherwise ok. Marasperse CB 45 Do. Marasperse CB 45 Do. Maraspersc C (c 100 Li5 Crumbly, very poor adhesion. Indulin A (sulfate lignin) 50 40 Very poor adhesion and cohesion Indulin A 100 40 D0. Bentnnito 5() 42 Asbestol (brous magnesium silicate) 50 42 l Compositions 11 and 12 were made by blending in a sigma mixer for 15 minutes. 2 Compositions 13 and 11i were very sticky.

Formulation No. 9 of Table IV was cured into sheets. Liners 0.037. inch in thickness were cut from these sheets and inserted in lacquered shells without the use of anl adhesive. Soda Water (Canada Dry) bottles (6 oz.) were chilled to 4 C., uncapped and recapped with the prepared crowns. The bottles were cycled between room temperature and 75 C. live times over a period of live days Paper flock, calcium carbonate and cork fines Were further tested as fillers for plastisols, in preparing cured sheets. The fillers were added to the plastisol, mixed one minute in an Aster blender, and the viscosity of the blend cured at 150 C. for one minute. Only the calciumcarbonate gave plastisols of a desirable low viscosity. The results are shown in Table V below..

TABLE V Fillers for PVC Formulation: Parts Exon 654 100 Sant. B1G 100 Cal. stcarate 3 Filler as indicated Filler Quantity Viscosity, cps. Remarks 1 Cork f1ncs 40 parts Bulk vol. of 40 g. cork was S00 ml.

The plastisol formed a coating around cork. The cured sheet rcsembled cork liner in appearance. Similar to No. l

80 parts White, medium hard sheet.

50 parts 5,500 at 38 C 1U parts. 26,600 at 44 C- Paper ilock Straw-colored sheet.

measured. Sheets 0.075 inch thick of each mix were.

Linears made from a sheet of the cork fines filled plastisol of No. 1 (Table V), 0.075 thick were cycled Without leakage. The cork nes had a particle size less than 2 mm. Liners of this type are commercially attractive, as they employ a normally waste product, name 1y, the cork nes.

Polymers containing chlorine, such as polyvinyl chloride, for example, decompose to some extent with the formation of undesirable decomposition products, such as hydrogen chloride, at elevated temperatures. Accordingly, it is frequently desirable to add a small amount of stabilizer to prevent such decomposition and consequent discoloration. The stabilizer should be non-toxic if the liner containing it is intended for use in bottling beverages. The stabilizers in Table V were tested for their stabilizing effect on Exon 654 upon heating 15 minutes at 170 C. Calcium stearato, a non-toxic stabilizer was found to give excellent results, particularly, at 3% concentration, based on the resin. Sodium bicarbonate gave good results, although not as good as calcium stearate. However, sodium bicarbonate is a foaming agent and it has the advantage that it can serve the dual function of stabilizer and foaming agent in preparing foamed vinyl chloride plastisol liners. Dibutyl tin oxide also gave excellent results as did mixtures of sodium bicarbonate with either calcium stearate or dibutyl tin oxide. Foaming with the bicarbonate was suppressed to a considerable extent by using such mixtures.

0.025 parts=0. 5% of resin. 0.075 parts=1. 5% of resin. 0. parts=3% of resin.

It has been found that the plycerol ester of hydrogen` ated rosin reduces the migration of the plasticizer in unfoamed polyvinyl chloride plastisols. In general, 5 to 10% of the plycerol ester is employe-d, based on the As previously indicated, the use of foamed polyvinyl `chloride plastisols gives liners with outstanding properties. Various blowing agents were effective, some more so than others. Typical blowing agents have been pointed out previously. Blowing agents based on organic nitrogen compounds, which liberate free nitrogen, generally produced good foam but may, in some instances, impart odor or off flavor and, consequently, be undesirable for many uses for this reason.- They also, in some instances, produced foamed sheets which were discolored yellow which again may be undesirable for some purposes.

As will be appreciated, curing time and pressure of cure affect uniformity and lneness of porosity. Preferably, the curing time is between 1/10 minute and 1/2 minute, the pressure between 0 lb./sq. inch and 500 lbs/sq.

Stabilizer Percent of Appearance of product resin 1 Control, no stabilizer Dark brown. 2 Calcium stearate 0.1 o. 3.-- o 0.5 Medium brown. 4- do-. 1. 5 Amber. 5. o 3 Light cream. G V-l-N (A strontium con- 0. 1 Medium dark brown.-

taining compound described on page 32 of Stabilizers publ. by Advance Solvents & Clemical Corp.

Medium brown.

o. Light cream.

C1101 vivi Center cream, edges tau. Medium dark browu.

o. Center tan, edges black. Center light tan, some black around Light tan, slight foaming.

Deep cream, considerable foaming. Deep cream, slightly more foaming. Deep cream, about same as #23 regard- }Light color, slight foaming. }Light color, no foaming.

Stannous stearate proved to be an unsatisfactory stabilizer, even at 3% on the resin for protecting Exon 654. It can be used to some extent in other formulations.

Stayrite No. 90 protected this resin against discoloration at the 3% level.

Therrnolit-e No. 3l is an even better stabilizer, 1.5%

inch, and the temperature between 130 C. and 180 C.,` although the temperature is not generally critical. Naturally, there will be some variation in these values,`de

pending on the particular blowing agent employed.

Foams, based upon the use of water or aqueous bicarbonate solution, were improved by employing emulsitiers` l which aid in the formation of water-in-oil emulsions.

Such emulsiers include the materials recited below as Wellas those mentioned previously. VThe nonionicemulsiiiers in general are preferred.

Specific emulsiers of this type, which proved satisfactory in forming foamed sheets with a density of 0.6 grams/cc., using ammonium bicarbonate solution as a blowing agent, are Triton X-177 (an alkylphenoxy-polyether alcohol), nonylphenyl ether of polyethylene glycol, Ethofat -15 (a higher fatty acid, including caprylic acid, stearic acid, intermediate acids between these two acids, and oleic acid-ethylene oxide condensate), Ethomid 60-15 (a condensate similar to Ethofat 60-15, but with the acids replaced by their amides), Tergitol NPX (an alkylphenyl polyethylene glycol ether), Methocel 4000 c.p.s. V(methyl cellulose) and Elvanol 50-42 (polyvinyl alcohol).

Liners cut from cured sheets foarned with aqueous ammonium bicarbonate or with Vynafoam were inserted in lacquered shells. The liners were 0.037 inch in thickness and no adhesive was used. There was no pressure loss when bottles of Canada Dry carbonated water were recycled ive times between room temperature and C., employing these crowns.

The following Table VII illustrates that, for satisfactory blowing, conditions should be controlled. The best results are illustrated by Nos. 33 and 34. As is evident from No. 32, merely bubbling Dry Ice through the plasticizer did not give a good blow.

TABLE F 0a med P VC Sheets of foamed polyvinyl chloride were prepared by the following procedure: Surface active agent and blowing agent were added to 100.75 grams of plastisol in an Oster blender and mixed 30 seconds. l5 grams of the i-i5 ticizer, it is desirable to introduce the carbon dioxide under pressure as disclosed hereinafter.

As previously indicated, curing temperature has little or no effect on the density of foam in the normal tem- -perature range in foaming polyvinyl chloride plastisols with aqueous ammonium bicarbonate solutions. Foams cured at 110 C. had a density of 0.66 grams/cc., whereas those cured from the same composition at 150 C. had a density of 0.62 grams/ cc.

The ratio of resin to plasticizer, however, is an important factor in preparing good foams. For example, with ratios of polyvinyl chloride (Exon 654) to Santicizer B-16 of 100: 100; 100:80 and 100:60, the densities of the foams were 0.62; 0.74 and 0.85, respectively. It is desirable that the density of the foamed resin be between about 0.4 gm./cc. and 0.8 gm./cc., preferably between 0.5 and 0.7 grd/cc. For this reason, the amount of plasticizer, based on the resin, should normally be between parts and 125 parts per 100 parts of resin and, preferably, at least parts per 100 parts of resin.

While the type of plasticizer affects the density, this effect is associated with the viscosity of the plastisol. The low viscosity plasticizers, such as dioctyl phthalate and acetyl tributyl citrate, yield foams with a density of 0.54 to 0.55 gn'L/cc., whereas those of higher viscosity,

VII

plastisols resulting mixture were cured in the mold with an 0.037 x 5 x 5 cavity at the indicated temperature, time, and total pressure on the mold surfaces.

Formulation of plastisol:

Grams Exon 654 Santieizer B--16 50 Dibutyl tin oxide 0.75

Surface active agent, g. Blowing agent, grams Temp., Time, Press., Dens Size of Remarks C. min. lbs. pores 2.5 NHiHCOa 130 12 1,000 1.14 Coarse Uneven loam,

Water, 5 130 M 1,000 N o foaming. 0.8 g. NHil-ICOQ, in 5 g. H2O 120 M 500 0. 83 Coarse- Uneven.

do 120 M 18 No learning.

do 120 M Uneven. do 120 M Even. do 140 M Somewhat uneven. do 130 M Very uneven. do 130 M Even, g. N 1141-1003 in 12.5 ml. H2O 130 M Very poor tear strength. 1.6 g. NI-IiI-ICOS 120 M 100 1.13 Irregular Nearly solid.

do. 120 M 50 1. 05 o Do. do. 150 M 1, 000 0.95 Coarse. Uneven.

g. N1 120 V 1, 000 1. 86 No foaming.

do 130 M 500 l. 2 D0. do 130 1 g 100 0.85 Uneven. do 130 1 500 Very uneven. do 170 M 500 Do. do M 500 Even. do 130 M 100 0. 73 D0. do M 100 0.70 D0. 0 4 g. NH4 H2O 120 1 2 100 0.91 D0. Same as 21 except plasticizer was Santieizer 141. 120 M 100 0. 81 Somewhat uneven. Tergitol NPX, 1 0.16 g. NH4HOO3 in 5 lf H2O 120 M 100 Do. do do 120 M 50 0. 80 D0.

db- 0.4 g. N H4HCO3 120 M 100 0. 96 Nearly even.

do do M 100 0.91 Uneven. do 120 1 100 0.85 Nearly even. do 10 ml chilled carbonate 120 M 100 0. 96 Even.

o M 200 1. 14 Uneven. None 2.4 g. NH4HCO3 in 15 g. Hz 120 M 100 0. 69 do Do. do Dry Ice bubbled through plas 120 1 100 1. 12 Opaque sheet, very hour (Santieizer B-l). little foaming. Elvauol 50-42, 0.1 0.8 g. NH4HCO3 in 10 g. H2O 120 1 100 0. 55 Medium- Even. Methocel 4,000 e.p.s., 0 l 120 1 100 0. 58 do Do. None 5 g BL353 130 M 500 0.68 do Even, yellowish. do do 170 M 500 1. O5 ...do Uneven. do do. gg gg 1. 03 Coarse Even. do 5 g. Unieel ND 170 M 500 0. 82 Medium. Even, odor of formaldehyde. do 5 g. Unieel ND. 2.5 g. urea. 120 V 500 1.24 Fine Even, sparse, poor. .do do- M 500 0. 98 Medium. Even.

While carbon dioxide is much more soluble in many of the plasticizers employed than it is in water, still for good results employing carbonV dioxide dissolved in the plassuch as Santicizers B-16 and 141 yield foams with densities of 0.70 to 0.74 under identical conditions. In

general, foams with densities of 0.5 to 0.7 gm./cc. can` be prepared with any of the plasticizers giving a viscosity of below 25,000 c.p.s. when employed in equal amounts, based on the resin, by adjusting the amount of blowing agent, although, preferably, the viscosity should be below polymethylsiloxane) can be employed. Alternatively, stearic acid can be incorporated into the plastisols at concentrations of 2.5% to to prevent sticking of plastisol to the hot mold without affecting adhesion of the 15,000, as previously indicated. 5 foam to the Unichiome-coated shells adversely. Butyl Typlflal OTHIUHIOQS, USfHg lmmomllm blCafbOnate lS stearate was similarly effected as a mold release agent a b W1Ug agent, are g1V11.11Tab 1@VIHbe10V/ 'Thef 1S and, like stearic acid, is nontoxic, but :stearic acid is also included one formulation, using carbon dioxide Withpreferred in its Overall Characteristics For example out Pressure' The formulations Included' butyl stearate served Well as a mold release agent for Exon 654 100 grams. l0 plastisols pressured at 250 p.s.i. carbon dioxide, but was Stayrite No. 90 2 grams. inferior to stearic acid at 500 p.s.i. Butyl stearate was Plasticizer As indlcated. less satisfactory as a replacement for the primary plas- Suffafle QCUVC agent AS mqfcatei ticizer in the range of 5 to 20%, as liners employing it, BOWIUg agent AS lncllcildlr in some instances, leaked during the cycling test.

The Compositions were cured as 0.0375 inch times 5 o Mold P1essure and temperature at time 0f Cure had inch times 5 inch sheets in a Carver press, little effect on the density of the foam. The pressure of TABLE VIII Foamed PVC liners, without CO2 pressure Surface Curing Curing Curing Plasticizer Amount, active Amount, Blowing agent Amount temp., press., time, Delis. Size Remarks grains agent grains deg. lbs. min. pores 1 B-l 100 Cyclohexauol 40 g 150 100 1 Small Neaysolid sheet sat. with with strong odor CO2 at STP. of eyclohexanoL 2...-- B-l 100 Triton 2 16% NH4 101110.... 100 110 1 0.06 Medium. Evensheet.

X-IO HCOa aqueous sollution.

100 do 2 10 m1 120 100 i 0.72 --.do Do.

10o d0 2 i0 m1. 130 100 1 0.83 do Do.

ino o 2 i0ni1 150 100 i 0.62 do Do.

100 do 2 10 160 100 1 0.82 do Somewhat sparse,

uneven pores.

80 do 2 10m1 150 100 1 0.74 do Evensheet.

60 o 2 10ml 1.50 1CD 1 0.85 Fine Very even pores,

rather hard sheet.

9 Saut.141 80 do 2 10 ni1 150 100 1 0.70 Medium Nearly even sheet. 10. DOI 80 do 2 10ml 150 100 0.55 Large. @pen poi-es, very even sheet. 11..-. Acetyltri- 80 do 2 10ml 150 100 1 0.54 Medium Open pores, even.

butyl citrate. 12 do 60 do- 2 10m1 150 100 1 0.55 Large Slightlyuneven. 13. do 60 do 2 5ml 150 100 1 0.72 Fine Evensheet.

Liners cut from cured sheets of a polyvinyl chloride plastisol foamed with ammonium bicarbonate, eg., #5, in Table VIII, applied to shells and cycled tive times between 2 C. and 75 C. showed no leakage.

Superior results were obtained by charging the plastisol 100 parts in a 750 part bomb with carbon dioxide at a pressure of 250 p.s.i. at room temperature until equilibrium was established. About mn. with shaking was required. The carbon dioxide saturated plastisol, in an amount of about 0.30 grain per shell, was then injected into Unichrome coated, unlacquered shells at room temperature. The shells containing the plastisol were then placed in a mold, maintained at 170 C., and shaped and cured by contact with a hot plunger for 5 seconds. Curing was almost instaneous at 170 C. Either a stepped or regular plunger can be employed. The heating can be varied between 100 C. and 200 C. In place of carbon dioxide, other inert, non-toxic gases can be employed, but carbon dioxide is preferred, especially in preparin'g liners for caps for carbonated beverage containers.

Alternatively, sheets of the carbon dioxide pressurized plastisols could be prepared by injection and curing in 0.0375 inch times 5 inch times 5 inch molds and liners cut`from 'the sheets and inserted in the Caps.

To prevent sticking to the mold, conventional release agents, such as Dow Cornings silicone release fluid (a carbon dioxide applied for saturation of the plastisols was the dominant factor regulating density of foam. Density decreased with increase in pressure up to 250 p.s.i. With little change in density or uniformity in porosity at higher pressures up to 500 p.s.i. The minimum suitable carbon dioxide pressure is p.s.i. and, preferably, it should be at leastv 200 'p.s.i. The use of 250 p.s.i. and 500 p.s.i. carbon dioxide resulted in liners having excellent cycling properties.

Little or no foaming occurs upon release of the pressurized plastisol into the cap. In normal operation foaming does not occur until the pressurized plastisol in the cap is subjected to heat. The fact that a foam does not normally result until after the plastisol is positioned in the cap is advantageous as it permits more ready control of the shaping of the liner.

The use of carbon dioxide under pressure is illustrated in Table IX below. In Astt 1 to 5, 19 and 20, sheets of liner 0.0375 inch times 5 inch times 5 inch were prepared, while in 6 to 18, the composition was cured directly as a cap liner, The general formulation is:

Carbon dioxide Pressure as indicated.

TABLE IX F Gamed PVC llners wzt/z C02 pressure Amount, l Amount, CO2 Temp., Press., Dens. Av. Wt. Size of Plastlcizer g. Lubricant g. Press. deg. Time lbs. of sheet cap liner, Peres Remarks 250 130 1 min Even loam.

250 130 1 min D0.

250 150 1 min D0.

125 150 1 min- D0.

125 170 1 min D0.

250 150 30 sec Liner very adherent to uniclirorne treated cap, also stuck to mold after several caps.

125 150 30 sec (1) O. 88 0. 54 do Do.

250 170 30 sec (1) O. 88 0. 35 d0 D0.

250 170 5 sce. (1) 0.35 d0 Weak, incomplete eure. Stuck to mold after several caps.

250 170 5-30 sec 2 (1) 0.35 do Apparently complete n eure. Stuck to mold F after several caps. 250 110 5-30 scc.2 (1) do Fair adhesion to cap.

- No adhesion to mold.

12 B-16 100 .do 5 250 170 5-30 sec.2 (1) do Good adhesion to cap.

Stuck to mold after 1 several caps.

13 B-lf 100 Steam acid. 5 250 170 530 see.2 (1) do Very good adhesion to cap, no adhesion to mold.

14 B-16 100 do 3.5 250 170 5-30 sec.2 (1) 0.30 do Very good adhesion to cap; slight tendency to adhere to mold.

15 B-l 100 .-.dOr 2. 5 250 170 5-30 500.2 (1) do Adhered to mold.

16 B-le 100 Peltghte 5 250 170 5-30 see.2 (1) do D0.

17 Sant. 14l 100 Stearie acid 5 250 170 5-30 sec.2 (1) 0.25 do Good adhesion te cap;

some tendency to adhere to mold. 18 Acetyl tri- 100 do 5 250 170 5-30 sec.2 (1) 0.28 d0 Excellent adhesion to b utyl cap; no radhesion to Acitret.. 50 mold.

ce y ri- Very good adhesion to 19 butyl do 5 250 170 5-30 sec.2 (1) 0. 46 0.32 do cap; no adhesion to citrate. mold. Sant. B-l6 50 Acetyl tri- 75 20.-.-. butyl 10 5 250 170 5-30 sc (l) 0.51 o. 29 do Excellent adhesion to entrate. cap; no adhesion to Sant. B-16.- mold 1 Weight of plunger.

2 Cap cured in mold 5 seconds, removed, kept at curing temperature 30 seconds longer.

Foamed liners were tested for bottle leakage in the five time cycling between 2 C. and 75 C. over a period of tive days. No leakage was observed with any of the liners tested. The liners were prepared by charging the carbon dioxide saturated plastisol into the Unichrome coated shells and shaping and curing with a hot plunger in the manner previously indicated. Typical formulations with results are:

Liner composition:

Exon c54 1'00 Acetyl tributyl citrate.. 100 Stayrite No. 90 2 Foarned at 250 p.s.i. CO2.

Weight of Shoulder Pressure after Pressure liner, g. thickness cy g expected,

inches p.s.i.

1 0.28 0. 046 66 p.s.i. at 30 C 65-73 2 0.28 0. 046 58 p.s.i. at 30 C.- -73 3 0.28 0. 046 v67 p.s.i. at 30 C 65-73 Note-,None leaked.

Liner composition: G.

Exon 654 100 Santicizer B-16 100 Stayrite No. 00 2 Foarned at 250 p.s.i. CO2.

Weight of Shoulder Pressure alter Pressure liner, g. thickness cycling expected,

inches psi.

0.35 0. 045 68 p.s.i. at 30 C (S5-73 0. 0. 046 72 p.s.i. at 30 C 65-73 0.35 0. 046 G3 p.s.. at 30 C (l5-73 NOTE-None leaked.

Liners cut from Vynafoam foamed sheets of polyvinyl chloride plastisols and from talc-filled plastisols, such as those used in the cycling test, were also tested for water absorption. The liners, after weighing, were immersed in chilled bottles of Canada Dry soda water, capped and cycled five times between 2 C. and 75 C. The liners were removed, the ysurfaces blotted dry with filter paper and weighed. The water adsorption of the Vynafoam liners was 3.2% and that of the talc-lled liner 3.7%, both of which Values are excellent.

' In `a further series, plastisols of polyvinyl chloride were pressurized in a bomb at 250 p.s.i. and 500 p.s.i. with carbon dioxide. Lacquered shells were primed with Uniichrome 2l9 PX or Goodrich A'458-B and baked live minutes at C. The shells were then injection filled with plastisol, molded, foamed and cured in live seconds at 170 C. in the regular crown mold. The lined crowns were removed from the mold and placed on heated platens for 30 seconds to insure uniformity of cure throughout the mass of the liner. In the following Table X, Unichrome was used as the adhesive in Nos. l to 5, and Goodrich A 458-B in the remaining numbers. The general formulation:

TABLE X Plasticlzer Amount, Additives Amount, CO3 Adhesion Adhesion Wt., liner, Thickness Thickness Density 1 grains grams Press. to cap to mold grams shoulder center Stearicaeid 4 250 V.good None. 0.30 0.046 0.018 0.70 4 do 0. 45 0. 046 0. 018 4 0. 51 0. 046 0. 018 5g 0.46-0. 60 0. 046 0. 018 0.9

250 do 0.20 0.046 0. 01s 0. 53 100 Butylstearate". 5 500 do Adhered 0. G1 100 Stearie acid 5 500 .--do None 0.30 0. 046 0.018 5 500 .--d0 ..-do 0. 23 0.043 0.015 0.64

5 0. 34 0. 065 0. 030 0. 67 11 do 5 0. 22 0. 0116 0.018 0. 59 12 Di-isobutyl 5 0.38 0.065 0.035 0.03

adipate.

13 do 150 --d9 5 0.22 0.046 0.018 14 do 150 {tacfc C jjj 10g 0. 43 0. 046 0. 01s 0. 09

1 Density estimated from weight and volume of cured foamed material in crown.

Liners corresponding to liners Nos. l, 2, and 3 in Table X were cycled five times between ice water temperature (1.5 to 2 C.) and 75 C. without leakage.

The inclusion of talc, 20 to 30% by weight, in a plastisol containing equal amounts of polyvinyl chloride resin and plasticizer (Santicizer B-16) roamed without too great an increase in viscosity and without detrimental eect on the liner properties. Liners containing 20% talc (No. 4 in Table X) did not leak in the cycling test between 1.5 C. and 75 C.

Liners foamed in place by pressuring the plastisols at 500 p.s.i. did not withstand cycling nearly as well. Thus, of 8 bottles capped with liners No. 8 of Table X, six leaked; of 13 bottles capped with liner No. 9 of Table X, ten leaked; of l bottles capped with liner No. 10 ot Table X, four leaked and of 8 bottles capped with liner No. 1l of Table X, four leaked.

With the carbon dioxide foam, the minimum weight of the liner should be 0.3 grams and the maximum weight 0.7 grams, in the conventional crowns employed today which have a bottom inside diameter of about one inch. If a liner is formed with a center depression, normally the diameter of the center depression is about A; inch. However, other size center depressions, e.g. 7/8 inch, can be employed.

Vinyl resin modified unsaturated alkyd resins also are eiective as liners. For example, a styrenated unsaturated alkyd, such as Reichholds Polylite Resin 8150 (the specic composition being 50% styrene, 50% alkyd resin) was catalyzed with 0.5% benzoyl peroxide, cast into a mold and polymerized minutes at 130 C. Liners, 0.037 inch thick, were cut from the flexible sheets and placed in lacquered crown shells. No adhesive was employed. Bottles of Canada Dry water capped with these crowns withstood iive cycles between room temperature and 75 C. without leakage.

Such ethylenically unsaturated resin modified linear alkyds should be flexible. Other examples of such resins are styrene to 70%)-diethylene glycol tumaratesuccinate, styrene ethylene glycol maleate, the corresponding methyl methacrylate modilied resins, Vibrins (Naugatuck) unsaturated polyester resins, to 75% polystyrene; Selectrons (Pittsburgh Plate Glass); Sinco resin (Synder Chemical); Stytol resin, chlorostyrene-unsaturated polyesters; and (Kappers) vinyl toluene-unsaturated polyesters.

DuPont polythene PM-l and PM-l cross-linked with benzoyl peroxide were molded into crown caps in the same manner as the plastisols. Irrathene (irradiated polyethylene) could not be molded directly into crown caps, because of its infusibility and high shrinkage. However, sheets of Irrathene can be produced by pressure molding (10,000 p.s.i.) at 130 C., liners cut from the sheet and the liners adhered to the cap by rubber cement.

Liners of peroxide free radical modified polyethylene y not improve its performance as a liner.

gave performance on the above cycling test, although leakage was noticed in an occasional cap. Polyethylene plasticized with natural rubber, 20 parts polyethylene to 10 parts rubber, resulted in liners which could be molded in the crown shell either with or without peroxide induced cures. The resultant liners had excellent physical properties. The range of rubber to polyethylene can be from one part to 50 parts of rubber per 100 parts of polyethylene.

In place of natural rubber, there can be employed an equal amount of an olefin or dioleiin hydrocarbon type synthetic rubber. Either homopolymers or copolymers of these materials with each other or with other unsaturated hydrocarbons can be employed. Examples of such rubbers are butadiene-styrene copolymer (GR-S) and isoprene-isobutylene copolymer (butyl rubber). When a peroxide curing agent is employed, it is used in an amount of 0.5% to 15%, preferably 10%, based on the polyethylene.

Sheets were molded from polyethylene (PM-1), irradiated polyethylene (Irrathene) and polyethylene plasticized with low Mooney (ML 4-20) unvulcanized, natural rubber and polyethylene cross-linked with peroxide free-radicals, specifically 0.1% methyl ethyl ketone peroxide together with 0.1% colbaltoctoate. Linerswere cut from these 'sheets and placed in lacquered shells without the use of an adhesive. Bottles of Canada Dry soda Water were capped with the crowns and tested through five cycles between 2 C. and 75 C. The bottles with polyethylene (PM-d) liners (39 mils) held up fairly well under the rigorous test conditions, although some slight leakage was noted in three out of eight bottles on the iirst cycle. Employing one part of natural rubber as a plasticizer with two parts of the polyethylene (PM-1) did The peroxide cross-linked polyethlene gave excellent results in the cycling test.

Sheets of thickness 0.037 inch and 0.075 inch were molded from polyethylenes of different molecular weights and were cut into discs and cemented to shells using Bondmaster L 255 (Rubber and Asbestos Corporation) as an adhesive Alternatively, there can be employed natural or synthetic, eg., GR-S, rubber cement.

Surprisingly, it was found that the higher molecular weight polyethylenes gave inferior results to lower molecular weight polyethylenes. Bakelite DYN] (mol. weight :24,000) developed many more leaks than (Du Pont) PM-l (mol. weight-18,000 to 19,000) with the thinner liner, and the thicker liners from DYNI were even poorer in that virtually all `of them developed leaks in the 2 to 75 C. cycling test. Preferably, when uncured polyethylene is used as a liner, the molecular weight should be in the range of 8,000 to 20,000, e.g., Alathon A, mol Weight 18,000 to 19,000; Alathon B, mol weight 16,000 to 17,000; Alathon C, mol weight 12,000 to 13,000; Ala- Vthon D, m01 weight 8,000 to 9,000.

. in the machine.

However, when cured polyethylene (cured with a peroxide, such as benzoyl peroxide, or with X-rays or ultraviolet light) is employed, considerably higher molecular weights can be used, for example, up to 100,000.

While GE Irrathene 101 lgave fair results when Cast into Sheets of 0.0375 inch as a liner in the cycling test, considerable improvement was noted if the centers of liners made from this material were removed, the resulting rings plied against a disc of the same material, and the resultant liners molded directly into the crown caps, using Bondmaster No. L 255 as an adhesive. The products prepared were still not as good as the foamed polyvinyl chloride plastisols. Irrathenes with a different degree of irradiation from Irrathene 101 can also be employed.

As previously indicated, polyethylene cross-linked by peroxide free-radicals gives excellent results in the cycling tests. Cross-linking at too high a temperature results in occasional failure, due to polymer degradation. The use of a cross-linking temperature tof 70 C., however, results in a tough, high modulus polyethylene with a softening point as high as 134 C.

Under the appropriate conditions, closed cell polyethlene foams of density 0.5 to 0.6 gram/cc. can be formed into excellent liners. Several alternative methods can be employed to form such foams.

(l) A solution of an organic blowing agent, e.g., azobis isobutyronitrile, in an amount of one gram per V200 cc. \of hot benezene solution, containing 2O grams of polyethylene, is cast and the solvent evaporated to form a film. The product is then foamed in a mold under pressure, e.g., 500 p.s.i., at a temperature above the fusion point of polyethylene, e.g., 170 C., for about one minute.

y(2) Finely divided polyethylene (one to 100 microns in greatest dimension) is intimately mixed with finely divided inorganic or organic blowing agents (0.2 to 100 microns in greatest dimension), such as sodium bicarbonate, ammonium carbonate, ammonium bicarbonate and/or a zobis isobutyronitrile, using 5 to 50 parts of blowing agent to 100 parts of polyethylene. The dry mixture is poured into a mold, the mold closed under moderate to high pressure, e.g., to 500 p.s.i., and the mixture is foamed by heating at a temperature above the fusion point of the polyethylene and the decomposition point of the blowing agent, e.g., 140 to 170 C., for a period of time from 10 seconds to 2 minutes.

Centrifuged natural rubber latex of 60% solids preserved with ammonia was measured into lacquered shells to give liners having a shoulder thickness of (a) 19 mils and (b) 28 mils. The latex was evaporated to dryness in the shells at 70 C. Bottles of Canada Dry soda water were capped with these crowns and cycled as above. The bottles with caps containing 0.4 gram of latex, resulting in a liner weight of 0.24 gram (19 mils), all leaked bad- 1y, while bottles with the caps containing 0.6 gram of latex, resulting in a liner weight of 0.36 gram and a thickness of 28 mils, did not leak. Adhesion to the crowns was excellent. However, Water absorption was quite high, due to the non-rubber solids present in the latex. The distribution of the injected plastisol is an important feature of the present invention, as can now be appreciate-d. In some cases, the pl-astisol, after injection into the center area of the cap, does not spread radially and uniformly over the interior surface thereof in reaching out to meet the circumferential wall of said cap. The surface concavity of the cap (5%. in. radius) serves as a gravity barrier preventing complete lateral movement of the plastisol so that, in effect, the iiuid deposit may be irregularly `shaped and of gibbous definition which is influenced by the high speed forward travel of the shells Under these conditions, after the cap has passed into the curing and molding dial, the plastisol,

Vbeing controlled to an exact volume, frequently does not assume the .full contour of the plunger, leaving a strip void in the peripheral area of the cured liner on one side and squeezing upward by reason of localized excess into .'the iiuted skirt on the side directly opposite thereto.

Whenever this condition arises, the crowns must be scrapped.

`To overcome these defects provision was mode to cause the plastisol, while being injected into the capV at or near its center, to be centrifugally impelled toward the circumferential wall of said cap, uniformly of distribution being controlled by the speed of rotation, eg., about 600 to 2000 rpm., preferably, 1000 rpm. The rpm. is preferably increased `in proportion to the increase in viscosity. The spreading time required by this centrifugal distribution can be lbetween about 0.05 and 0.2 second, and is dependent upon the speed of the liner-forming machine, i.e., the longer time being used with the slower speed of the machine. The complete fluid coverage over the entire interior horizontal surf-ace of the cap facilitates and insures quality molding of the material at high speed. Scrap is virtually eliminated thereby.

Experience teaches that the greater the speed of operation, the more delicate the control must be. Control is commensurate with speed. In order, therefore, to make the operation practical and economical sound, the finest points of control are embodied in the plastic liner molding assembly unit. Itis also preferably that the various steps in the process be incorporated into a single machine, for separate and distinct operations develop costs proportionately. The method of this application is, therefore, a continuous one embodying in sequence the several steps of manufacutre in one composite unit.

As described above, partial yor complete precuring of the plastisol :before molding is advantageous. The injected plastisol, having been laterally dispersed in all directions over the concave interior surface of the cap, is subjected to radiant heat which impinges merely on the exposed plastisol surface thereby forming a tack-free surface film, leaving the under-portion still in a tacky condition. The exposure time to the radiant heat is between about 2 and 4 second, depending upon the speed of the machine. This procedure is necessary to offset any tendency of the material to stick to the molding punch Iand to permit low molding pressures. Pinpoint deposits, left on the molding punch, act as foci for further 'build-up of material.

I, Since the thermal life for a vinyl chloride plastisol, for

example, is extremely short, these deposits decompose on the punch and redeposit lon subsequent liners 'during molding or adhere tenaciously thereto, resulting in said liners fbeing forcibly pulled out of the shell when the punch is retracted at the ejector station.

An alternate method we have found for eliminating the above-mentioned sticking tendency, is to effect full cure of the plastisol in the cap under radiant heat prior to molding under heat and pressure. tained in a few seconds, the speed of cure depending on the intensity of the heat source. Higher pressures, however, are Vusually required for molding a fully cured plastisol than is demanded for one that is but partially cured. After hot molding of the yfully cured plastisol, adhesion thereof to the lacquered shell is of substantially the same order 0f magnitude as that after hot molding of the totally uncuredor partially cured plastisol.

For purposes of illustration, the cap shells may be at room temperature but preferably are heated somewhat above room temperature to reduce viscosity of the plastisol when the latter is injected into the same. The plastisol is injected into the heated caps while the caps are rotating in their plane of travel and is centrifugally dispersed from the area lof material introduction to extend Circumferentially and engage the shell wall, thereby covering substantially the entire interior surface of the shell. The shells are rotated at a speed from 600 to 2000 rpm., which speed is variable and correlated with the viscosity of the plastisol, a preferred speed of rotation being about lFull cure is at-V 1000 r.p.m. The particular plastisol used had the following composition:`

The rotating of the shell to centrifugally distribute the plastisol as a coating on the interior of the shell will usually take from 0.05 to 0.2 second, depending upon the r.p.m. and viscosity of the plastisol, the higher the speed, the shorter the time period required t-o produce the liner. Thereupon the shell, with the liner therein, is heated, preferably by the use of any suitable radiant heating means, being exposed thereto from about 2 to 4 seconds, and until the temperature of the metal shell and the liner material reaches a temperature from about 150 to 275 F., preferably about 180 F. Thereupon, the liner, having a substantially tack-free surface produced by the aforesaid exposure to radiant heating, is subjected to a curing and molding under pressure, as above-described. Preferably, the curing and molding time will be from 6 to 12 seconds, and the pressure will vary from to 150 p.s.i., depending upon the extent ofthe precuring, the curing and molding being conducted under a temperature of from abou-t 325 to 380 F.

The following composition:

B Exon 654 56.00 Geon 202 4.00 Dioctyl phthalate 50.00 G-62 5.00 Staybelite No. 10 5.00

was formed as a liner, as just above-described, except that the radiant heat was conducted to give the shell and liner material a temperature of 300 to 375 F., prefer- `ably 350 F., and the molding `and curing time was less, namely, 4 to 10 seconds, since the radiant heating produced a substantially complete pre-curing. The pressure employed to form the liner varied from 150 to 350 p.s.i. and the temperature varied from 325 to 380 F.

In addition to the compositions above referred t-o, the following compositions were also operated with satisfactory result-s:

Geon 202, as indicated previously in the specification, has a molecular weight much lower than that of Exon 654. The use of such a low molecular weight polyvinyl chloride, eg., 50,000 or less, together with a higher molecular weight polyvinyl chloride, is especially advantageous as the lower molecular weight polymer aids in 26 plasticizing the high molecular weight polymer, increases the shelf life of the plasticol, and improves the adhesion of the higher molecular weight polymer to the shell. This is true whether or not the shell has a lacquer coating on it.

We claim:

1. A container closure comprising a shell having a cushion liner comprising a roamed vinyl chloride polymer plastisol, including a mold lubricant in the liner.

2. The container closure of claim 1, including stearic acid as a mold lubricant.

3. A container closure comprising a shell having a cushion liner comprising a vinyl chloride polymer plastisol containing a plasticizer and including the glycerol ester of hydrogenated rosin to reduce migration of the plasticizer.

4. A container closure comprising a shell having a cushion liner including a high molecular weight vinyl chloride resin and a low molecular weight vinyl chloride resin in an amount suiicient to increase the adhesiveness of the composition to the shell.

5. A container closure comprising a shell having a cushion liner comprising a vinyl chloride polymer plastisol and also including a mold lubricant in the liner.

6. A container closure according to claim 5 wherein said cushion liner also includes a plasticizer and the glycerol ester of hydrogenated rosin to reduce migraion of the plasticizer.

References Cited by the Examiner UNITED STATES PATENTS 1,149,200 8/15 La Porte 154-89 1,427,133 8/ 22 Taliaferi'o. 1,486,937 3/ 24 Taliaferro. 1,858,279 5/32 Parker 154-89 1,956,012 4/34 Egan 264-268 2,047,497 7/36 Studt 260-93.5 2,114,308 4/ 38 McGowan et al. 2,149,532 3/39 McManus 21S-40 2,238,681 4/41 Dorough 21S-38 2,383,839 8/45 Beeldey 260-45.5 2,389,761 11/45 Burgeni 21S-40 2,427,699 9/ 47 Aronovsky et al 215-40 2,477,316 7/49 Sparks et al 260-45.5 2,489,407 1.1/ 49 Foye. 2,514,195 7/50 Kuhn 260-92.3 2,528,506 lil/50 fi-oye. 2,548,305 4/51 Gora. 2,581,926 1/52 Groten et al. 2,597,378 5/52 Rogers et al. 2,654,913 10/53 Maier 18-59 2,663,908 12/53 Maier et al. 2,666,036 1/54 Schemencke 264-50 X 2,684,774 7/54 Aichele 21S-40 2,688,776 9/54 Evans et al. 18-59 2,689,840 9/ 54 Husum et al. 2,700,186 1/55 Stover 264-268 2,714,748 8/55 Stirnemann et al. 18-48 2,719,564 10/55 Schneider. 2,796,189 6/57 Cooke et al. 21S-40 2,823,422 2/ 58 Schneider 264-268 2,835,926 5/58 Maier et al. 264-268 2,840,858 7/58 Rainer et al. 3,090,772 5/ 63 Crowell 260-75 OTHER REFERENCES Baird: P.V.C. Paste,7 British Plastics, April 1948, pp. 167-171.

THERON E. CONDON, Primary Examiner. EARLE I. DRUMMOND, Examiner. 

1. A CONTAINER CLOSURE COMPRISING A SHELL HAVING A CUSHION LINER COMPRISING A FOAMED VINYL CHLORIDE POLYMER PLASTISOL, INCLUDING A MOLD LUBRICANT IN THE LINER. 